Process for countercurrent extraction of vegetable material by sequential contactingof the material with mutually-miscible high-aquosity and lowaquosity organic solvents



Sept 21, 1965 J. B. o'HARA ETAL PROCESS FOR GOUNTERGURRENT EXTRACTION OF VEGETABLE MATERIAL BY SEQUENTIAL CONTACTING OF THE MATERIAL WITH MUTUALLY-MISCIBLE HIGH-AQUOSITY AND LOW-AQUOSITY ORGANIC SOLVENTS med April s. 1961 United States Patent O PROCESS FOR COUN'I'ERCURREN'I EXTRACTION OF VEGETABLE MATERIAL BY SEQUENTIAL CONTACTING F THE MATERIAL WITH MII- TUALLY-MISCIBLE HIGH-AQUOSITY AND LOW- AQUOSITY ORGANIC SOLVEN'IS James B. OHara and Arthur E. Sclroepfer, Decatur, Ill.,

assignors to A. E. Staley Manufacturing Company, *De- `catur, Ill., a corporation of Delaware Filed Apr. 3, 1961, Ser. No. 100,200 6 Claims. (CI. Zoll-123.5)

The present invention relates generally to extracting soluble matter from solid material by the use of a mixed solvent liquid. More specifically, it relates to certain improvements and innovations in the production of soy protein concentrate by extracting non-protein components from defatted or oil-free soybean flakes, meal or ilour with aqueous lower alcohols.

It is well known to move a stream of material countercurrent to a solvent liquid for extracting solubles into the liquid and providing a residual solid wet with fresh liquid, usually volatile, so that the wetting liquid may be removed by evaporation. Among these processes are those in which the solvent liquid is a mixed solvent, such as an aqueous alcohol, or an aqueous mixture of two or more alcohols, or an aqueous mixture of an alcohol and another liquid, such as acetone or benzol.

Where a mixed solvent is employed, the residual wetted solids in certain instances are more retentive of one or more components of the solvent than of another or others. Sometimes there is difficulty in removing all, or substantially all, traces of one or more such components in the process of drying the wetted solids. For example, in the cases where water is a component, certain solids, such as proteinaceous, cellulosic, or starchy materials may be more retentive yof the w-ater than of other components. Such greater retention of water makes it more diflicult and costly to dry out the water by use of heat, and in some cases, the amount of water retained may be such that high temperature must be avoided in removing it, to avoid changes in the solids. In extracting protein, such as defatted soybean flakes, with aqueous alcohol of high aquosity, the protein selectively removes water from the solvent and swells. This renders masses of the akes more compact or caked and less easily penetrated by the solvent. The discharge of such swollen solids from the solvent results in difficulty in removing the water as mentioned above. Furthermore, the resulting product is diflicult to handle on mechanical conveyors and cannot be dried etiiciently.

The object of the invention, generally stated, is to avoid these and other disadvantages encountered in the countercurrent extractions with mixed solvents, particularly in the extraction of non-protein components of oil-free or defatted soybean flakes, meal or flour with aqueous alcohol.

The invention contemplates the formation of the desired mixed solvent within the counter-moving streams of solid and liquid solvent, by introducing a stream of one component of the mixed solvent to the stream of residual solids leaving the system, and introducing a stream of the remaining component of the mixed solvent to the stream of solid material at a region in its path of travel intermediate its entrance and exit in the system. This method or technique of introducing the solvent components is referred to herein as the split solvent method.

An important object of the invention is to subject solids of the class described to the extracting action of a solvent liquid of changing composition such that with respect to one component of a mixed solvent or a combination of more than one, but not all of the components, there is a substantial increase in concentration as the countercurrent flows proceed.

Another important object of the invention is in subjecting material of the class described to extraction by an aqueous mixed solvent liquid, to decrease the aquosity of the liquid toward the exit for the residual solids.

Another important object of the invention is to pass solids, which selectively remove water from a mixed aqueous solvent, through a body of liquid solvent of composition changing from relatively higher aquosity at the entrance for the solids to a relatively lower aquosity `at the exit for the solids, the lower aquosity being such as to remove water selectively acquired.

An important and more specific object of the invention is to improve the production of soy protein concentrate by employing the above-mentioned split solvent method in extracting non-protein components from defatted or oil-free soybean flakes, meal or flour with aqueous lower alcohol solutions, thereby minimizing swelling and facilitating penetration of the soybean material, reducing the in-put load on the desolventizing equipment, and reducing the heat requirements for desolventizing.

Certain other objects of the invention will, in part, be obvious and will in part appear hereinafter.

For a more complete understanding of the nature and scope of the invention reference may now be had to the following detailed description thereof, taken in connection with the accompanying drawing wherein the single ligure is a flow-diagram illustrating one working embodiment of the invention.

The present invention is particularly useful in the production of soy protein concentrate from the residue of extracting oil from soybean flakes by use of hexane or other solvents used in the so-called solvent extraction process. Such residue is commonly designated as I-flakes or F-flakes in the soybean processing industry, the former being the industrial grade of flakes and the latter being the food grade. The main dilference is that the I-flakes are toasted at lower temperatures and therefore show less toasting and Ia higher content of soluble protein. Such flakes contain protein, carbohydrates, ash, fiber and minor quantities of other materials. In order to up-grade such flakes in protein and to remove other solubles and ladverse taste-ingredients, they have been subjected to aqueous aliphatic monohydric alcohol, particularly methanol. This is effective to remove carbohydrates and to increase the content of protein to upwardly from about by weight.

Such an extraction may be carried out by a wide range of aqueous methanol, for example, from 35% to 65% methanol by volume, and at temperatures, for example, in the range from to 140 F. Increasing the temperature increases the rate of extraction. Increasing the aquosity also increases the rate of extraction but decreases the yield of recoverable and saleable protein in the soybean concentrate fraction.

It has been found that when the extraction is carried out in the conventional countercurrent ow of the de- 3 fatted or oil-free soybean material and of aqueous methlanol, increasing the aquosity from 35% water by volume to 50% and more, causes swelling of the protein by absorption of water. This results in caking and where caking is induced the solvent does not penetrate but acts only at the surface of caked material. In consequence, where caking is encountered, the soybean material is so moved or agitated as to increase contact with the solvent.

The discharge residue carries this absorbed water with it, and to dry it out increases the heat load and the time of drying.

By the split solvent method of the present invention, using methanol or other lower alcohol, the I-fiakes, F- flakes or other soybean material move first through the exiting aqueous methanol, then through a region wherein this solvent is formed, and then through a region wherein the methanol or alcohol content is highest in the system, and preferably, sufficiently high to dewater the swollen protein. As a result, the discharge carries less volatiles (i.e., alcohol plus water) to the desolventizing step to follow. Of great importance is the fact that product discharging from the extraction step can be easily handled on mechanical conveyors and efficiently dried.

In a comparative study of the single-stream and splitstream extractions, it has been found that 100 parts by weight of I-flakes when drained infiate to 214 to 235 parts in leaving a single-stream extraction but only to 170 parts in leaving a split-stream extraction, wherein water is one stream and 80.5 volume percent methanol is the other, in proportion to form 60 volume percent aqueous methanol. The product discharging from the single-stream extraction process is something like cooked oatmeal, in which condition it is extremely ditcult to handle and has very poor drying characteristics.

Referring now to FIG. 1, it will be understood that the invention is not limited to or by the illustrative embodiment of material or apparatus shown therein, which is an as sembly of standard types of equipment. Numeral represents a supply of soybean material, i.e., I-fiakes, F-flakes, soybean meal, or soy flour, for a measuring feeder 12 of known type which introduces the akes or other material into the top end 16 of an extraction tank or tower 14. Tank 14 is shown vertically elongated to aid in breaking up the flakes as they move from the top toward the bottom end 18 of the tank. This is accomplished in one known way by a series of staggered or off-set traveling screens 20, of which six are shown with each one arranged one to drop its contents onto the one below. Thus, any caked material is broken up as it falls. Preferably, steam coils are located beneath each traveling screen so as to elevate the temperature of the solvent flowing upwardly through the extractor.

Into the vicinity of the bottom 18 of the tank 14 is fed a low aquosity alcohol, for example, one which is 80.5 percent volume of methanol. This enters via feed line 22 from one of two solvent make-up tanks 24, a metering pump 25 being used to feed the solvent at a predetermined rate.

Into a region intermediate the ends of the tank, such as the middle 26 as shown, is fed either water or a high aquosity methanol-water mixture via feed line 28 and metering pump 27 from a supply 30. The rates of feed in lines 22 and 28 are such as to form on mixing aqueous methanol of 60% by volume. This is merely illustrative within a permissible range at least as low as and and at least as high as 65 volume percent of methanol. For the 60 volume percent referred to, the preferred temperature is 135 F., which is illustrative of suitable temperatures at least as low as 90 F., and at least as high as 140 F.

Although the discharged residue is the product aimed for, both the liquid and the solid discharges from the tank 14 are treated for solvent recovery. The out-flowing liquid, or miscella, leaves tank 14 in the Vicinity of the top 16 via line 32 into a collecting tank 34 from which a pump 36 moves it as required through a filter 38 forming a clear filtrate in line 40 entering a still or evaporator 42.

4 The vapor or distillate is condensed in a condenser 44 and discharged via line 46 into a recycle solvent tank 48 from which it may be returned to the process via line 50 to the solvent make-up and feed tanks 24.

The extracted residue, which in the tank 14 has passed through the low aquosity alcohol entering via line 22, is removed from the vicinity of the bottom 18 by an endless drag conveyor 52 of known type operating in a closed drainage pipe 54 so that adhered liquid drains back into the tank 14 from an elevated drainage compartment 56. At this point, the drained extracted flakes consist of the desired protein product and carried or entrained methanol and water.

To remove and conserve solvent and to facilitate drying, the wet flakes are passed through a desolventizer, represented graphically by three steam jacketed units 58, 60 and 62, in which the material is moved along in known manner by worm screws. Line 64 from unit 58 and line 66 from unit 62 carry solvent vapors to a condenser 68 which discharges condensate through line 70 into the recycle solvent tank 48.

The desolventizer is preferably not used fully to dry the flakes therein, but to reduce the volatiles to about 10 to 12%. The residue then passes by line 72 into the upper end of an inclined rotary drum drier 74 through which it passes countercurrent to a stream of air 76 at 240 F. to 320 F., which reduces the volatiles to 7 to 10% in the final protein concentrate discharged into the storage bin 78.

The concentrate has a protein content upwardly from about 70% (dry substancebasis) and the protein recovery based on the protein content of the infeed of Lflakes is upwardly from (d.s.b.).

Having reference to FIG. 1, the following example illustrates one way in which the invention has been practiced on a pilot-plant scale.

Example 1 I-fiakes were fed into the top of tank 14 at the rate of pounds per hour. Water was introduced through line 28 at the rate of 4.8 gallons per hour, and 80.5 percent by volume methanol was introduced through line 22 at the rate of 31.4 gallons per hour. The solvent velocity upwardly through the tank 14 was at the rate of about 5.5 feet per hour. The room temperature of the pilot-plant was about 70 F. with the temperature of the solvent flow ing through the extractor being about F. The screens 20 traveled at speeds of about 0.2 feet per minute, except the bottom screen which was set slower so as to accumulate sufficient solid material in the extractor to maintain solid, continuous pattern. Wet material was removed from the bottom of the tank 14 by the conveyor at a rate sufficient to equal the rate of feed of flakes into the top. Steam was supplied to the jacketed units 58, 60 and 62 at a pressure of 30 p.s.i.g. and the drained material was moved therethrough at a speed of about 1.0 foot per minute. Hot air at a temperature of about 239 C. was introduced into the lower end of the drier drum 74 at the rate of 800 cubic feet per minute. The product entered the drum drier at a temperature of about F., and discharged therefrom at a temperature of about 200 F. The rate of discharge was approximately 75 pounds per hour and the soy protein concentrate product was at least substantially free of solvent (i.e., not over 1.0% by weight) and had a moisture content of about 9.0%.

Example 2 The procedure of Example 1 was repeated but instead of using the split solvent technique, all the liquid solvent containing percent methanol was introduced through line 22 at the rate of 0.5 gallon per minute. It was found that the drained material entering the desolventizer had a volatile content of 68.8% by Weight of which 56.2% was methanol, whereas in Example 1 these values were 60.2% and 67.9%, respectively. The weight of material entering the desolventizer in Example 2 was about 2.35 times the weight of I-akes entering the extractor whereas in Example 1 this ratio was substantially lower, being only about 1.7. This difference was due to the greater water retention in Example 2, which in turn placed a proportionally greater load on the desolventizing and drying equipment. Even though the alcohol retention in Example l may be somewhat higher than in Example 2, the energy requirement for removing or reducing the volatiles content is substantially lower since the alcohol has a much lower energy requirement than water when vaporized.

In the pilot-plant in which Examples l and 2 were carried lout the principal pieces of operating equipment had the following sizes or capacities: The extractor tank or tower 14 was 9.1 inches high, 24 inches wide, and 6 inches deep, giving a cubic capacity of 13,100 cubic inches. The jacketed screw conveyors S8, 60 and 62 were each ten feet long and six inches in internal diameter. The inclined drum drier 74 was 10 feet long and 30 inches in diameter. The .pilot-plant was capable of producing finished soy protein concentrate product at the rate of 65 to 75 pounds per hour based on the weight of the product discharged from the drier 74. Obviously, a number of changes can be made in the apparatus. First of all, it can be increased in size and capaci-ty to a plant scale installation. The various pieces of equipment may be modified or replaced with different types known to design chemical engineers.

Likewise, a number of changes may be made in the process conditions used in Examples 1 and 2. As aboveindicated, there are permissible ranges of concentration of the aqueous alcohol solvent used, extraction temperatures, and drying temperatures. Instead of using methanol, other lower alcohols may be used such as ethanol, propanol, and butanol, lor various mixtures thereof.

The process is not limited to the extraction of nonprotein solubles from defatted soybean materials.

As indicated above, it has application to the solvent treatment of other materials which exhibit the same or similar extraction characteristics.

Since the invention may be practiced in various ways, besides the embodiments specifically described above and the indicated variations thereof, all matter described above is intended to be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. The method of solvent extraction of defatted vegetable material subject to extraction of soluble content therefrom by a solvent liquid comprising a compatible mixture of water and volatile, Water-soluble organic solvent capable of dissolving non-protein components of said defatted vegetable material, which comprises continuously moving a stream of said material in one direction through a liquid-con-iining space, introducing said material in the vicinity of the first end of said space to said solvent mixture moving countercurrent to said material, removing the undissolved residue of said material from the vicinity of the second end of said space, forming said solvent liquid within said space in the vicinity` of a region intermediate to said ends in part by introducing into said space in the vicinity of said second end a less aqueous liquid selected from the group consisting of said organic solvent and a mixture of water and said organic solvent and moving .said less aqueous liquid toward said intermediate region, and in part by introducing into said region a more aqueous liquid selected from 'the gnoup consisting of water and a mixture of water and said organic solvent, whereby extraction by said :aqueous solvent liquid takes place between said region and said rst end, and whereby the undissolved residue of said extraction is in part at least dewatered by the less aqueous liquid between said region and said second end, and removing the loaded solvent liquid from the vicinity of said ltirs-t end.

2. The method of solvent extraction of defatted soybean material subject to extraction of soluble content therefrom by a solvent liquid comprising a compatible mixture of water and volatile, water-soluble orga-nic solvent capable of dissolving non-protein components of said defatted soybean material, which comprises continuously moving a stream of said material in one direction through a liquid-coniining space, introducing said material in the vicinity of the first end of said space to said solvent mixture moving countercurrent to said material, removing the undissolved residue of said material from the second end of said space, forming said solvent liquid within said space in the vicinity of a region intermediate to said ends in part by introducing into said space in the vicinity of said second end a liquid selected from the group consisting of said organic solvent and a mixture of water and said organic solvent having a lower aquosity than said solvent liquid and moving the same toward said intermediate region, and in part by introducing into said region a liquid selected from the group consisting of water and a mixture of water and said organic solvent which has a higher aquosity than said solvent liquid, whereby extraction by said aqueous solvent takes place between said region and said iirst end, and whereby the undissolved soy residue of said extraction is in part at least dewatered by the less aqueous liquid between said region and said second end, and removing the loaded solvent liquid from the vicinity of said rst end.

3. The method of solvent extraction of defatted soybean material subject to extraction of soluble content therefrom by an aqueous solvent liquid comprising a compatible mixture of water and volatile, water-soluble lower alcohols capable of dissolving non-protein components of said defatted soybean material, which comprises continuously moving a stream of said material in one direction through a liquid-confining space, introducing said material in the vicinity of the iirst end of said space to said solvent mixture moving counter-current to said material, removing the undissolved residue of said material from the second end of said space, forming said solvent liquid within said space in the vicinity of a region intermediate to said ends in part by introducing into said space in the vicinity of said second end a liquid selected from the group consisting of lower alcohols and a mixture of water and lower alcohols having a lower aquosity than said aqueous solvent liquid and` moving the same toward said intermediate region, and in part by introducing into said region a liquid selected from the group consisting of wat-er and a mixture of water and lower alcohols which has a higher aquosity than said aqueous solvent liquid, whereby extraction by said aqueous solvent takes place between said region and said rst end, and whereby the undissolved soy residue of said extraction is in part at least dew-atered by the less aqueous liquid between said region and said second end, and removing the loaded solvent liquid from the vicinity of said rst end.

4. The method of solvent extraction of defatted soybean material with aqueous methanol, which comprises ycontinuously moving a stream of said material in one direction through a liquid-conning space, introducing said material in the vicinity of the first end of said space to said aqueous methanol moving countercurrent to said material, removing the undissolved residue of said material from the second end of said space, forming said aqueous methanol within said space in the vicinity of a region intermediate to said ends in part by introducing into said space in the vicinity of said second end a liquid selected from the group consisting of methanol and a mixture of water and methanol having a lower aquosity than said extracting aqueous methanol and moving the same toward said intermediate regio-n, and in part by introducing into said region a liquid selected from the group consisting of water and a mixture of water and methanol which has a higher aquosity than said extracting aqueous methanol, whereby extraction by said aqueous methanol takes place between said region and said first end, and whereby the undissolved soy residue of said extraction is in part at least dewatered by the liquid between said region and said second end, and removing the loaded solvent liquid from the vicinity of said first end.

5. The method of claim 4 wherein said extracting aqueous methanol has a methanol content within the range of about 35 to about 65 percent by volume, said liquid introduced in the vicinity of said second end has a methanol content of at least about 75 percent by Volume, and said extraction is carried out within said space in the temperature range `ot from about 90-140 F,

6. The method of claim 4 wherein said liquid selected from the group consisting of water and a mixture of water and methanol which has a higher aquosity than said extracting aqueous methanol is introduced approximately midway between said ends.

References Cited by the Examiner UNITED STATES PATENTS 1,114,018 10/14 Moore 23--310 2,495,706 1/50 De Voss et al 260-123.5 2,635,094 4/53 Belter et al. 260-123.5 2,812,232 11/57 Delaplaine 23-310 OTHER REFERENCES Belter et al., 659 O.G. 1-106-07, 1952 (abstract of application Serial No. 138,528).

WILLIAM H. SHORT, Primary Exmnner.

L. ZITVER, Examiner. 

1. THE METHOD OF SOLVENT EXTRACTION OF DEFATTED VEGETABLE MATERIAL SUBJECT TO EXTRACTION OF SOLUBLE CONTENT THEREFROM BY A SOLVENT LIQUID COMPRISING A COMPATIBLE MIXTURE OF WATER AND VOLATILE, WATER-SOLUBLE ORGANIC SOLVENT CAPABLE OF DISSOLVING NON-PROTEIN COMPONENTS OF SAID DEFATTED VEGATABLE MATERIAL, WHICH COMPRISES CONTINOUSLY MOVING A STREAM OF SAID MATERIAL IN ONE DIRECTION THROUGH A LIQUID-CONFINING SPACE, INTRODUCING SAID MATERIAL IN THE VICINITY OF THE FIRST END OF SAID SPACE TO SAID SOLVENT MIXTURE MOVING COUNTERCURRENT TO SAID MATERIAL, REMOVING THE UNDISSOLVED RESIDUE OF SAID MATERIAL FROM THE VICINITY OF THE SECOND END OF SAID SPACE, FORMING SAID SOLVENT LIQUID WITHIN SAID SPACE IN THE VICINITY OF A REGION INTERMEDIATE TO SAID ENDS IN PART BY INTRODUCING INTO SAID SPACE IN THE VICINITY OF SAID SECOND END A LESS AQUEOUS LIQUID SELECTED FROM THE GROUP CONSISTING OF SAID SOLVENT AND A MIXTURE OF WATER AND SAID ORGANIC SOLVENT AND MOVING SAID LESS AQUEOUS LIQUID TOWARD SAID INTERMEDIATE REGION, AND IN PART BY INTRODUCING INTO SAID REGION A MORE AQUEOUS LIQUID SELECTED FROM THE GROUP CONSISTING OF WATER AND A MIXTURE OF WATER AND SAID ORGANIC SOLVENT, WHEREBY EXTRACTION BY SAID 